As a detection technique of hexavalent chromium, Patent Document 1 discloses a detector including an elution portion for eluting hexavalent chromium and a reaction portion which reacts with eluted hexavalent chromium. In the detector, the elution portion and the reaction portion are stacked on each other. The elution portion holds water and chemicals. The reaction portion contains a color change agent. When a sample comes into contact with a surface of the elution portion, the reaction portion changes in color. By detecting the color change, the presence or absence of hexavalent chromium in the sample is qualitatively measured. Patent Document 1: Japanese Patent Application Publication No. 2007-139497